There have been reports of an issue in which the error “Subtask CheckPrereqs execution failed: Check Tenant Prerequisites” is received when running Hybrid Configuration Wizard. Microsoft recently released a fix to remediate impact.
Symptoms:
When you use the Hybrid Configuration wizard to create or manage a hybrid environment that contains Microsoft Exchange Server 2013, you receive the following error message:
Subtask CheckPrereqs execution failed: Check Tenant Prerequisites
Deserialization fails due to one SerializationException:
Microsoft.Exchange.Compliance.Serialization.Formatters.BlockedTypeException: The type to be (de)serialized is not allowed: Microsoft.Exchange.Data.Directory.DirectoryBackendType
Cause:
This problem occurs because of recent changes to Exchange Online that prevent the Exchange 2013 Hybrid Configuration wizard from running correctly.
Resolution:
Download and install the latest cumulative update for Exchange 2013.
Hybrid Exchange 2013 Server Configuration Validation
1. From the Exchange 2013 PowerShell run Test-FederationTrust –userIdentity ckent@domain.com The output should look like the one below.
2. From the Exchange 2013 PowerShell run Test-FederationTrust –userIdentity (Onpremiseuser@domain.com). The output should be similar to the above.
3. Now run Get-Organizationrelationship |FL to check the Organization relationship and the output should look like the screenshot below.
4. Connect to Office 365 using the following script:
5. From Office 365 PowerShell, verify the TargetSharingEpr field is populated.
6. Once both servers are updated verify to see if you are able to view the free/busy information between the on-premise users and cloud users.
7. If you are still not able to do so, then you should run the Hybrid configuration wizard following the steps below:
8. Check to see if you are able to view Free/busy information.